Hybridized compressor

ABSTRACT

An air compressor includes a first compressor stage and at least one motor. The first compressor stage includes a first housing, a first drive plate, and a plurality of first pistons. The first drive plate is positioned in the first housing and includes an odd number of first lobes. The plurality of first pistons each contact the first drive plate at different locations relative to top dead center on the first lobes. The at least one motor is operable to rotate the first drive plate to move the plurality of first pistons to generate a volume of compressed air in the first housing.

TECHNICAL FIELD

The present disclosure is directed to air compressor systems, and more particularly directed to hybrid air compressor systems operable using multiple independent power (e.g., torque) sources.

BACKGROUND

Some types of fuel delivery systems require a source of compressed air to properly deliver fuel to the cylinder for combustion. The compressed air it typically provided by the engine or a compressor component operated by the engine. Challenges exist related to providing a source of compressed air at constant or near constant pressure for use in the fuel delivery system.

Various types of compressors may be used to provide a consistent, steady flow of compressed air for use as an oxidant in a fuel delivery system. Crank and rod piston style, swash plate style or scroll-type compressor are all potential compressor options. Each of these types of compressors has certain drawbacks. For example, a scroll-type compressor typically is unable to provide enough pressure and flow rate to meet the demands of a fuel delivery system. Swash plate compressors typically consume significant energy as a result of the friction inherent to the design. Regular crank and rod piston type compressors require significant height in order to achieve desired pressure and flow levels, which may be problematic due to limited space available for the compressor in an engine compartment of a vehicle. Further, each of the above-described compressors are typically difficult to scale up or down to meet specific pressure and flow requirements for different applications.

SUMMARY

The principles described herein may address some of the above-described deficiencies and others. One aspect provides an air compressor comprising a first compressor stage and at least one motor. The first compressor stage includes a first housing, a first drive plate, and a plurality of first pistons. The first drive plate is positioned in the first housing and includes an odd number of first lobes. The plurality of first pistons each contact the first drive plate at different locations relative to top dead center on the first lobes. The at least one motor is operable to rotate the first drive plate to move the plurality of first pistons to generate a volume of compressed air in the first housing.

The at least one motor may include an electrically driven motor, a mechanically driven motor, and a controller, wherein the controller is operable to switch between the electrically driven motor and the mechanically driven motor depending on an operation state of the mechanically driven motor. The at least one motor may include an electrically driven motor and a mechanically driven motor, and the air compressor may further include a clutch operably positioned between the mechanically driven motor and the first drive plate. Only one of the plurality of first pistons may be positioned at top dead center position at a time. The plurality of first pistons may be evenly spaced apart circumferentially and the first lobes may be evenly spaced apart circumferentially. The plurality of first pistons may be oriented radially outward.

The air compressor may further include a second compressor stage, which includes a second housing, a second drive plate positioned in the second housing and comprising an odd number of second lobes, and a plurality of second pistons each contacting one of the second lobes at different locations relative to top dead center on the second lobes. The at least one motor may be operable to rotate the second drive plate to move the plurality of second pistons to generate a volume of compressed air in the second housing.

Only one of the plurality of first pistons and the plurality of second pistons may be positioned at top dead center at a time. The first and second compressor stages may be arranged coaxially. The at least one motor may operate the first and second compressor stages concurrently. The first and second housings may be coupled in flow communication with a single outlet of the air compressor.

Another aspect of the present disclosure relates to an air compressor system having a first drive plate, a plurality of first pistons, and an air chamber. The first drive plate includes a plurality of lobes arranged circumferentially. The plurality of first pistons are circumferentially spaced apart and in contact with the plurality of lobes. The air chamber is arranged to collect a volume of compressed air created by reciprocal motion of the plurality of first pistons when rotating the first drive plate. The air compressor system also includes an electrically driven motor operable to rotate the first drive plate, a mechanically driven motor operable to rotate the first drive plate, and a motor selection member configured to switch between the electrically driven motor and the mechanically driven motor as a source of torque for rotating the first drive plate.

The motor selection member may include or be configured to control a clutch. The plurality of first pistons may be positioned on separate ones of the plurality of lobes at different locations relative to top dead center on the plurality of lobes. The air compressor may further include a second drive plate and a plurality of second pistons. The second drive plate may include a plurality of lobes arranged circumferentially. The plurality of second pistons may be circumferentially spaced apart and in contact with the plurality of lobes of the second drive plate. The second drive plate may be driven by one of the electrically driven motor and the mechanically driven motor.

A further aspect of the present disclosure relates to a method of generating compressed air. The method includes providing a housing, at least one drive plate comprising a plurality of lobes arranged circumferentially, a plurality of pistons each contacting one of the plurality of lobes at different locations relative to top dead center, and at least one motor. The method further includes rotating the at least one drive plate to move the plurality of pistons radially to generate a volume of compressed air.

The at least one motor may include an electrically driven motor and a mechanically driven motor, and the method may include switching between the electrically driven motor and the mechanically driven motor based on a rotation speed of the mechanically driven motor. The method may include providing a pulley and drive shaft coupled to the at least one drive plate, and the mechanically driven motor may be coupled to the pulley with a belt. The electrically driven motor may be coupled to the at least one motor with a drive shaft. The method may include providing a controller and a clutch, wherein the controller operates the clutch to switch between the electrically driven motor and the mechanically driven motor as a power source for rotating the at least one drive plate.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate certain embodiments discussed below and are a part of the specification.

FIGS. 1 and 2 are perspective views of an example compressor assembly in accordance with the present disclosure.

FIG. 3 is a rear view of the compressor assembly of FIG. 1.

FIG. 4 is a side view of the compressor assembly of FIG. 1.

FIG. 5 is a front view of the compressor assembly of FIG. 1.

FIG. 6 is an exploded perspective view of the compressor assembly of FIG. 1.

FIG. 7 is another side view of the compressor assembly of FIG. 1.

FIG. 8 is a cross-sectional view of the compressor assembly of FIG. 7 taken along cross-section indicators 8-8.

FIG. 9 is a cross-sectional view of the compressor assembly of FIG. 7 taken along cross-section indicators 9-9.

FIG. 10 is a cross-sectional view of the compressor assembly of FIG. 7 taken along cross-section indicators 10-10.

FIG. 11 is a cross-sectional view of the compressor assembly of FIG. 3 taken along cross-section indicators 11-11.

FIG. 12 is a cross-sectional view of the compressor assembly of FIG. 3 taken along cross-section indicators 12-12.

FIGS. 13 and 14 are perspective views of another example compressor assembly in accordance with the present disclosure.

FIG. 15 is an exploded perspective view of the compressor assembly of FIG. 13.

FIG. 16 is a front view of the compressor assembly of FIG. 13.

FIG. 17 is a cross-sectional view of the compressor assembly of FIG. 16 taken along cross-section indicators 17-17.

FIG. 18 is a cross-sectional view of the compressor assembly of FIG. 16 taken along cross-section indicators 18-18.

FIG. 19 is a cross-sectional view of the compressor assembly of FIG. 16 taken along cross-section indicators 19-19.

FIG. 20 is schematic view of an example fuel delivery system in accordance with the present disclosure.

FIG. 21 shows a portion of another example compressor stage in accordance with the present disclosure.

FIG. 22 shows a graph representing pressure output provided by the compressor stage of FIG. 21.

FIG. 23 shows a portion of an example compressor stage for use in the compressor assembly of FIG. 1.

FIG. 24 shows a graph representing pressure output provided by the compressor stage of FIG. 23.

FIG. 25 is a graph showing pressure output for the compressor assembly of FIG. 16.

FIG. 26 is a schematic flow diagram showing a control strategy for operating the fuel delivery system of FIG. 20.

Throughout the drawings, identical reference characters and descriptions indicate similar, but not necessarily identical elements.

DETAILED DESCRIPTION

Illustrative embodiments and aspects are described below. It will, of course, be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions may be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.

The present disclosure is directed to a fixed or variable speed, flow rate controlled compressor. The compressor may be used to supply compressed air or other oxidant to a fuel preparation system, such as a dual fluid fuel injection system. An example dual fluid injection system and related methods is disclosed in U.S. Patent Publication No. 2011/0284652, which is incorporated herein in its entirety by this reference.

The compressor may be driven by one of two torque sources and is configured to switch between the two driving torque sources on command. In one example, one torque source is an electric motor packaged with the compressor features. The second torque source may be an engine driven motor, which operates the compressor via, for example, a belt and pulley drive system. In at least one example, the pulley may be arranged coaxially with an output shaft of the electric motor.

In one example, the compressor system may include a mechanically driven pulley, a clutch, a cam driven radial piston compressor, one-way inlet and outlet ports, and an electric motor operable to drive the compressor when no torque is applied via the pulley and associated engine driven (mechanical) motor. The compressor system may be architected in a functional layer configuration, which readily facilitates stacking compressor sections to increase capacity.

The compressor of the compressor system may include a radial piston construction driven by a rotating cam plate (e.g., a drive plate). The cam plate may include a cam track feature, which holds a follower driving a shaft connected to a piston. When the cam plate is rotated, the pistons follow the cam track via the follower and are moved radially outward, thus compressing a fluid (liquid or gaseous) by movement of the pistons. The follower may facilitate stable contact with the cam track with minimal lash.

The cam lift and duration may be designed to program or tailor the pressure pulse and duration. A plurality of pistons and cam track lift “lobes” on the drive plate may be employed to provide a combination that supplies a constant root mean square (RMS) pressure to the system. Timing of each compression event is controlled by the number of pistons and the number of cam lift events with the objective to have only a single piston at top dead center (TDC) position at a time. One piston at max compression, which corresponds with the TDC position, at a time also reduces the torque and power required to actuate the compressor.

Synchronized compression results in all pistons at full intake or compression simultaneously. FIG. 21 shows an example drive plate 230 having an even number of lobes 240 and an odd number of pistons 252A-C. A follower carried by the pistons 252A-C moves within track 242 such that the followers reach a TDC position at a peak of the lobes concurrently for each of the pistons 252A-C. This produces full range pressure pulses (0 to max pressure) in every cycle. A stable RMS flow and pressure require the addition of a pressure reservoir and regulator to produce a steady flow.

FIG. 22 shows a pressure output using the configuration of FIG. 21. The output pressure at its maximum point may be relatively high. However, a piston and cam configuration according to FIG. 21 allows all pistons at full compression simultaneously, thus producing pressure and flow spikes. With all pistons at full compression at the same time, torque to rotate the compressor is at its highest as well.

Sequential compression is provided by an unequal number of pistons and lobes according to, for example, the configuration of FIG. 23, which configuration is described in further detail with reference to FIGS. 1-19. The arrangement of FIG. 23 includes a drive plate 30 having an odd number of lobes 40 and a track 42. The configuration also includes an odd number of pistons 52A-C. Followers carried by the pistons 52A-C travel within the track 42. Only one of the pistons reaches TDC at a time.

Configurations such as the one shown in FIG. 23 provide an RMS pressure with minimized pressure pulses (from crossover to max pressure) during the pressure cycle as shown in FIG. 24. Separating or sequencing the pistons in compression order evens out the spinning torque and establishes an RMS pressure and flow rate. The RMS pressure and flow rate may be achieved without a restrictor or regulator. FIG. 24 shows a sustained pressure 7 less than the maximum pressure output when each piston reaches TDC. Programming the cam lobes to build pressure in each cylinder one at a time produces sequential compression events through the pressure cycle. With three pistons and five lobes, a sustained RMS pressure of about 70% to about 80% of the maximum pressure level may be achieved.

Adding additional stages to the compressor further equalizes the pressure pulses, thus raising the RMS pressure towards the maximum compression level. A two-stage compressor with three cylinders and five lobes in each stage may produce a sustained RMS pressure 7 of about 90% to about 95% of the maximum compression level, as shown in FIG. 25. Pressure pulsations are significantly reduced with this configuration. Adding a third stage would produce a sustained maximum pressure level with near zero pulsations. Each additional stage that is added is sequenced such that only one of the pistons achieves TDC positioning at a time.

With sequential compression, sustained flow and pressure rates may be optimized to run with minimal pulsations or ripple with addition of a simple restrictor or regulator as compared to those required for other types of compressor designs, thus reducing system complexity and cost.

The example compressors disclosed herein may be part of a fuel delivery system 2, as shown in FIG. 20. The fuel delivery system 2 may include an accumulator 3, a one-way valve 4, a fuel delivery device 5, a pressure regulator 6, and one of the compressor assemblies 10, 100 described below with reference to FIGS. 1-19. The compressor assembly 10, 100 operates to provide a flow of compressed air used to charge the accumulator 3. The compressed air is regulated with pressure regulator 6 as it flows to the fuel delivery device 5. The fuel delivery device 5 operates to combine a flow of air (e.g., oxidant) received from the accumulator 3 with a flow of fuel, and delivers the air/fuel mixture to a combustion chamber of an engine. The fuel delivery device 5 may include the dual fluid injection system and related methods disclosed in U.S. Patent Publication No. 2011/0284652 incorporated by reference above.

The compressor assemblies 10, 100 may be operated using one of an electric driven torque source (e.g., motor 14 shown in FIG. 6) or an engine driven torque source (e.g., motor 8 shown in FIG. 1) depending on, for example, an operation state of the engine. Typically, the engine driven torque source takes over providing torque to the compressor after the engine is operational and the engine driven torque source is operating at a speed needed to maintain output of the compressor system. The compressor assembly 10, 100 may include a controller to control switching between the torque sources. The controller may be referred to as a motor selection member or a torque source selection member.

FIG. 26 schematically shows a control strategy 300 for the fuel delivery system 2 shown in FIG. 20. The control strategy 300 begins by keying on controls initiation in a step 302 followed by checking compressor electric machine and clutch disengagement in a step 304. If the clutch is disengaged, a step 306 includes determining accumulator pressure required for engine start. If the pressure is not met, the step 308 includes engaging accumulator charge system followed by initiating an engine start sequence in a step 310. If the accumulator pressure is already met, the system moves directly from the step 306 to the step 310. After the engine start sequence is initiated, a step 312 includes determining a proper engine start. If the engine is not started, the system cycles back to step 306. If the engine is started, a step 306 includes engaging a compressor feed drive clutch and turning off the compressor electric machine in a step 316, followed by maintaining the engine running in a step 318.

Referring back to step 304, if the clutch is engaged and the electric machine is running, the system moves to a step 314 of disengaging the accumulator charge system, determining proper engine start in a step 312, and turning off the compressor electric machine and engaging the compressor feed drive clutch in the step 316.

Referring now to FIGS. 1-12, and in particular the exploded view of FIG. 6, an example compressor assembly 10 is shown including a first compressor stage 12, an electric motor 14, a transmission 16, a pulley 18, a casing 20, and inlet and outlet ports 22A, 22B. The compressor assembly 10 may also include a controller 24 and a clutch 26. The clutch 26 may be coupled via, for example, a belt 9 and pulley 18 to an engine driven motor 8. The engine driven motor 8 may operate after the engine is started using compressed air generated by operation of the compressor with the electric motor 14. The controller 24 may operate to switch between the electric motor 14 and the engine driven motor as torque sources for the compressor assembly 10.

The first compressor stage 12 includes a drive plate 30, a piston housing 32, a housing 34, an end plate 36, and three piston assemblies 38. The drive plate 30 includes a plurality of lobes 40 and a track 42. As discussed above, the drive plate 30 preferably includes an odd number of lobes 40, such as the five lobes shown in FIG. 6.

The piston housing 32 includes a central bore 44 and a plurality of piston bores 46. The number of piston bores 46 typically matches the number of piston assemblies 38. As described above, the compressor assembly 10 preferably includes an odd number of pistons such as three pistons, which correspond to three piston bores 46.

The housing 34 includes an air cavity 48 extending around a periphery of the piston housing 32. The air cavity 48 is aligned in flow communication with the piston bores 46. The air cavity 48 may include multiple circumferential channels extending around a periphery of the piston housing 32 as shown in FIGS. 11-12. The outlet openings 50A, 50B receive the inlet and outlet ports 22A, 22B as shown in FIG. 8.

The central bore 44 of the piston housing 32 receives the drive plate 30. The drive plate 30 encloses and may seal the piston housing 32 along one side thereof. An opposite side of the piston housing 32 is enclosed and may be sealed using the end plate 36.

The piston assemblies 38 each include one of the pistons 52A-C, one of the piston followers 54A-C, and a piston cover 56. The pistons 52A-C are positioned within the piston bores 46 of the piston housing 32. The piston followers 54A-C extend laterally from the pistons 52A-C (e.g., in an orientation parallel with a longitudinal axis of the compressor assembly 10) and are positioned within the track 42. The piston followers 54A-C may include a roller or other bearing surface, which provides reduced friction for the piston follower 54A-C as it travels within track 42. The piston cover 56 may facilitate flow into and out of the piston bores 46 to provide flow communication with the air cavity 48 of housing 34.

The entire first compressor stage 12 may be positioned within casing 20 as shown in FIGS. 11 and 12. The electric motor 14 may also be positioned within casing 20. The electric motor 14 may include an output shaft 60 as shown in FIGS. 11 and 12. The output shaft 60 may be operably coupled to the transmission 16. The transmission 16 may be operably coupled to the first compressor stage 12 via, for example, the drive plate 30. Operating the electric motor 14 creates rotational movement of components of the transmission 16, which rotates the drive plate 30. Rotating the drive plate 30 translates to radial movement of the pistons 52A-C within the piston bores 46 to create compressed air that travels out of the outlet port 22B. The inlet and outlet ports 22A, 22B may include one-way valves. The volume of compressed air may be used, for example, to charge an accumulator of a fuel delivery system as described above with reference to FIG. 20.

The transmission 16 includes an input gear 62, a sun gear 64, a plurality of planet gears 66, and a gear housing 68. The output shaft 60 of the electric motor 14 is coupled to the input gear 62 using, for example, a key or interference-fit connection. The teeth of the input gear 62 are engaged with teeth of the planet gears 66. Teeth of the planet gears 66 are engaged with teeth of the sun gear 64. The sun gear 64 maintains a fixed rotated position. The planet gears 66 are mounted to the drive plate 30 as shown in FIGS. 11 and 12. Rotating the input gear 62 causes the planet gears 66 to rotate about the input gear 62 and relative to the sun gear 64, thereby causing rotation of the drive plate 30. Changing the size (e.g., diameter) and numbers of teeth of the input gear 62, sun gear 64 and planet gears 66 may alter a gear ratio between the output shaft 60 of electric motor 14 and the drive plate 30.

Other types of transmissions, gear ratios and coupling mechanisms may be used to transfer torque output from the electric motor 14 to the drive plate 30. In one example, the output shaft 60 of the electric motor 14 is directly connected to the drive plate 30. In some arrangements, a clutch mechanism may be interposed between the drive plate 30 and electric motor 14.

The pulley 18 may be mounted to the compressor assembly 10 using a drive shaft 70. The drive shaft 70 may extend into engagement with the drive plate 30 from an opposite side of the drive plate 30 relative to the electric motor 14 (see FIGS. 11 and 12). A clutch 26 may be interposed between the drive shaft 70 and the pulley 18, as shown in FIGS. 11 and 12. The clutch 26 may include, for example, an over-running (e.g., Sprag) clutch. Several other example clutches (e.g., electro-magnetic, magneto-rheostatic, and electro-rheostatic clutches) available for use as clutch 26 are described below.

The clutch 26 may permit rotation of the drive shaft 70 without rotating the pulley 18, for example, during operation of the compressor assembly 10, using torque input from the electric motor 14 prior to an engine driven torque source being used to operate the pulley 18 to rotate the drive shaft 70. The clutch 26 may permit relative rotation between the pulley 18 and the drive shaft 70 until the pulley 18 is rotating at the same speed as the drive shaft 70 under power of the engine driven torque source. The controller 24 may operate to shut off the electric motor 14 so that torque input is provided solely by the engine driven torque source, which provides rotation of the drive shaft 70 to rotate the drive plate 30. The controller may operate automatically based on, for example, sensed operation of the engine driven torque source and compressed air output from the compressor assembly.

Referring to FIGS. 8-10, positioning of the pistons 52A-C and associated piston followers 54A-C relative to the drive plate 30 is described in further detail. Assuming that the drive plate 30 is rotating in a clockwise direction, the piston followers 54A-C and associated pistons 52A-C are arranged at different positions relative to the lobes 40, as shown in FIGS. 8 and 9. Piston follower 54A is shown approaching a bottom dead center (BDC) position between two adjacent lobes. Piston follower 54B is approaching TDC on one of the lobes 40. Piston follower 54C is moving off of TDC.

A maximum torque input is required in order to rotate the drive plate 30 as one of the piston followers 54A-C is approaching a TDC position. A maximum pressure output is also achieved when one of the piston followers 54A-C reaches a TDC position. FIG. 24 shows the pressure output of the compressor assembly 10, wherein each of the sinusoidal signals represent pressure output from one of the pistons 52A-C and associated piston follower 54A-C. A line 7 extending through the intersection points of the sinusoidal waves in FIG. 24 represents a sustained pressure level output for the compressor assembly 10. The sustained pressure level output for the single stage compressor assembly 10 may be about 70% to about 80% of the peak pressure output.

The level of sustained pressure output for a given compressor assembly may be increased by adding another compressor stage. Subsequent compressor stages added to a compressor assembly are timed such that there is equal time spacing between when any given piston is at TDC position. Adding additional compressor stages may increase the RMS pressure while not significantly increasing the momentary torque requirement in each one of the compression cycles. If the number of pistons and compressor stages are increased, there is a point at which a relatively steady state pressure output is possible with minimum fluctuation or pressure spikes. FIG. 25 shows the pressure output of a two-stage compressor assembly 100. FIG. 25 shows the sustained pressure output 7 much closer to the peak pressure output (e.g., about 90% to about 95%) as compared to the arrangement producing the pressure output shown in FIG. 24. Adding a third stage may increase the sustained pressure level even higher, as would adding a fourth, fifth or greater number of compressor stages.

Referring now to FIGS. 13-19, and particularly the exploded view of FIG. 15, a compressor assembly 100 is shown including a first compressor stage 112A, a second compressor stage 112B, an electric motor 114, a transmission 116, a pulley 118, a casing 120, inlet and outlet ports 122A, 122B, a controller 124, and a clutch 126. The first and second compressor stages 112A, 112B are arranged in axial sequence with each other as shown in FIGS. 15 and 17-19. The drive plates of the first and second compressor stages 112A, 112B may rotate about a common axis and be driven by a common drive shaft. The drive shaft may be powered by the electric motor 114 or a separate engine driven torque source (e.g., motor 8 shown in FIG. 1) coupled to the drive shaft via a belt (e.g., belt 9 shown in FIG. 1), pulley 118 and clutch 126.

The first compressor stage 112A includes a drive plate 130A, a piston housing 132A, a housing 134A, an end plate 136A, and a plurality of piston assemblies 138. The drive plate 130A includes a plurality of lobes 140A (e.g., five lobes) and a track 142A. The piston housing 132A includes a central bore 144A and a plurality of piston bores 146A (e.g., three piston bores). The housing 134A includes an air cavity 148A (see FIG. 17) and inlet and outlet openings coupled in flow communication with the inlet and outlet ports 122A, 122B. The piston assemblies 138 each include a plurality of pistons 152A-C, a plurality of piston followers 154A-C, and piston covers 156.

The second compressor stage 112B includes a drive plate 130B, a piston housing 132B, a housing 134B, an end plate 136B, and a plurality of piston assemblies 139. The drive plate 130B includes a plurality of lobes 140B (e.g., five lobes) and a track 142B. The piston housing 132B includes a central bore 144B and a plurality of piston bores 146B (e.g., three bores). The housing 134B includes an air cavity 148B (see FIG. 17) and inlet and outlet openings arranged in flow communication with the inlet and outlet ports 122A, 122B. The piston assemblies 139 each include a plurality of pistons 153A-C, a plurality of piston followers 155A-C, and a plurality of piston covers 156.

The electric motor 114 includes an output shaft 160 coupled to the transmission 116. The transmission 116 includes an input gear 162, a sun gear 164, a plurality of planet gears 166, and a gear housing 168. The transmission 116 may have similar features and functionality as transmission 16 described above. The transmission 116 is operably coupled to the drive plate 130A of first compressor stage 112A. The first and second compressor stages 112A, 112B are coupled together with a drive shaft 170 (see FIGS. 15 and 17-19). Rotating the drive plate 130A with the electric motor 114 and transmission 116 translates to concurrent rotation of the drive plate 130B.

The first and second compressor stages 112A, 112B, electric motor 114 and transmission 116 are positioned within the casing 120. The clutch 126 is interposed between the pulley 118 and the second compressor stage 112B, as shown in FIGS. 17-19. The controller 124 may monitor various parameters such as an engine speed, a rotation speed of pulley 118, and operation of electric motor 114 to determine when to shut off the electric motor 114 and switch to the engine driven torque source for driving of the first and second compressor stages 112A, 112B.

The clutch 126 may be configured as, for example, a rheological clutch, an electro-magnetic clutch, a magneto-rheostatic clutch, an electro-rheostatic clutch, or a over-running (e.g., Sprag) clutch. Details concerning at least some of these clutch options are provided in U.S. patent application Ser. No. ______ filed on ______, and entitled “Rheological Clutch Apparatus,” which patent application is incorporated herein in its entirety by this reference [the 46265.0144 application].

A basic clutch typically consists of drive and driven elements. Mechanical clutches utilize friction plates or pads, which are pulled or pressed into communication by an electromagnet. This method of actuation places the drive and driven elements into physical communication at full rotational speed and torque. The output speed and torque of the driven element is considered equal to that of the drive element.

In an electrically actuated (e.g., Rheological) clutch, the drive and driven elements are enclosed in chambers filled with a rheological fluid. A rheological fluid contains small magnetic particles, which when energized, increase the effective viscosity of the fluid. The rheological fluid is energized either magnetically with a field generated around the drive and driven elements, or directly by passing an electrical current through the rheological fluid between the drive and driven elements. In either case, the rheological fluid's effective viscosity is increased, causing torque to pass from the drive element to the driven element. Rheological fluid clutches may provide progressive engagement, through slip, which essentially yields a variable speed, and thus variable flow compressor output when the clutch is used with one of the compressor assemblies disclosed herein.

Rheological clutches may be employed as alternatives to a standard friction clutch. In the application of a compressor assembly as described herein, rheological clutches may act as or at least operate with variable speed or torque devices due to their ability to be gradually, partially charged, which allows a speed or torque differential between the drive and driven elements.

An industry standard electro-magnetic clutch may be integrated into the pulley (e.g., pulley 18) of a mechanical or engine driven input side of a compressor assembly. Energizing the clutch mechanism moves a friction plate attached to the rotating shaft of the compressor against the engine belt driven pulley (e.g., pulley 18) and connects the compressor to the running engine. Torque is transferred from the belt to the pulley and into the compressor shaft so that the compressor may continue rotation. The clutch may be actuated to transfer rotation of the pulley to rotation of the compressor shaft after turning off the electric motor of the compressor assembly.

A magneto-rheostatic (rheological) clutch may be employed to operatively connect the mechanical (e.g., engine driven) torque source to the compressor. Energizing an electromagnet situated around a closed volume of magneto-rheological fluid in which input and output torque elements are arranged energizes the magneto-rheological fluid to increase the viscosity of the fluid is increased, thereby causing the input drive element to transfer torque through the fluid to the output drive element and to the compressor. The output drive of the magneto-rheostatic clutch is attached to the rotating shaft of the compressor against the engine belt driven pulley (e.g., pulley 118) and connects the compressor to the running engine. This torque is transferred from the belt to the pulley, into the magneto-rheostatic clutch, and then to the compressor shaft (e.g., drive shaft 170). The compressor (e.g., first and second compressor stages 112A, 112B) components are rotated to generate compressed air.

An electro-rheostatic (rheological) clutch may be similar to the magneto-rheological clutch with the difference being at least in part related to the control method. An electrical voltage may be passed through the rheological fluid, thus charging the fluid particles. As the charge in the particles is increased, the effective viscosity of the fluid increases, thereby causing torque to be transferred from the drive element to the driven element. The mechanical function of the drive is substantially the same as the magneto-rheological clutch, with the difference related to the charging, or control, of the rheological fluid. The rheological fluid is directly communicated with control electrodes. An electrical current is passed through the rheological fluid via the electrodes to modulate the viscosity, thus controlling clutch engagement and torque throughput.

Over-running (e.g., Sprag) or one-way clutches may be utilized as a relatively effective, efficient and low cost alternative to controls actuated clutches such as the clutches described in the preceding paragraphs. Compressor operation with an over-running clutch may simplify operation. For example, when the engine, or other driving source, is in operation, the clutch is installed such that engagement between the drive pulley and the compressor shaft is enabled. When the electric machine is driving the compressor, the compressor shaft rotates in a direction of the pulley turning direction, thus “over-running” the clutch and disengaging the belt and pulley drive to allow the compressor to be driven solely by the electric machine. This arrangement allows engagement of the electric machine (e.g., electric motor 114) when there is no output from the belt and the belt is locked to the non-rotating driving source. When the drive element provides torque to the system, the over-running clutch engages and torque is transferred to the driven elements.

The hybridized compressor integration disclosed herein may include system control at a fundamental level. The state of charge of the system accumulator is typically monitored as described above with reference to FIGS. 20 and 26. On engine start, the control sequence of events includes system checks and automated switchover from external, or mechanical, start and stop of the compressor to electrical machine (electric motor) compressor drive for engine pre-start. Further details concerning such a control strategy are described above with reference to FIG. 26.

The systems and methods described herein may provide a unique compressor design that includes a dual torque source driven input compressor with a clutch for electric machine driven operation or mechanical drive. The systems and methods described herein may provide an improved piston and cam driver arrangement. The piston and cam arrangement may operate the compressor at a pre-defined RMS pressure and flow rate. A modular stackable design may facilitate configuration of multiple compressor stages without major modification or re-design. A potential advantage of the systems and methods described herein may include sustained RMS pressure and flow rates programmed into the architecture of the compressor. The systems and methods described herein may provide multiple compressor torque driven options. The options may be controlled using a controller based on engine operation and parameters associated with a fuel delivery system of the engine. The systems and methods may provide stackable compressor sections for easy expandability of the compressor to higher capacities. The compressor section arrangement may be designed to facilitate assembly (e.g., automated assembly).

The preceding description has been presented only to illustrate and describe certain aspects, embodiments, and examples of the principles claimed below. It is not intended to be exhaustive or to limit the described principles to any precise form disclosed. Many modifications and variations are possible in light of the above disclosure. Such modifications are contemplated by the inventor and within the scope of the claims. The scope of the principles described is defined by the following claims. 

What is claimed is:
 1. An air compressor, comprising: a first compressor stage comprising: a first housing; a first drive plate positioned in the first housing and comprising an odd number of first lobes; a plurality of first pistons each contacting the first drive plate at different locations relative to top dead center on the first lobes; at least one motor operable to rotate the first drive plate to move the plurality of first pistons to generate a volume of compressed air in the first housing.
 2. The air compressor of claim 1, wherein the at least one motor comprises an electrically driven motor, a mechanically driven motor, and a controller, the controller being operable to switch between the electrically driven motor and the mechanically driven motor depending on an operation state of the mechanically driven motor.
 3. The air compressor of claim 1, wherein the at least one motor comprises an electrically driven motor and a mechanically driven motor, the air compressor further comprising a clutch operably positioned between the mechanically driven motor and the first drive plate.
 4. The air compressor of claim 1, wherein only one of the plurality of first pistons is positioned at top dead center position at a time.
 5. The air compressor of claim 1, wherein the plurality of first pistons are evenly spaced apart circumferentially and the first lobes are evenly spaced apart circumferentially.
 6. The air compressor of claim 1, wherein the plurality of first pistons are oriented radially outward.
 7. The air compressor of claim 1, further comprising: a second compressor stage comprising: a second housing; a second drive plate positioned in the second housing and comprising an odd number of second lobes; a plurality of second pistons each contacting one of the second lobes at different locations relative to top dead center on the second lobes; wherein the at least one motor is operable to rotate the second drive plate to move the plurality of second pistons to generate a volume of compressed air in the second housing.
 8. The air compressor of claim 7, wherein only one of the plurality of first pistons and the plurality of second pistons are positioned at top dead center at a time.
 9. The air compressor of claim 7, wherein the first and second compressor stages are arranged coaxially.
 10. The air compressor of claim 7, wherein the at least one motor operates the first and second compressor stages concurrently.
 11. The air compressor of claim 7, wherein the first and second housings are coupled in flow communication with a single outlet of the air compressor.
 12. An air compressor system, comprising: a first drive plate having a plurality of lobes arranged circumferentially; a plurality of first pistons circumferentially spaced apart and in contact with the plurality of lobes; an air chamber arranged to collect a volume of compressed air created by reciprocal motion of the plurality of first pistons when rotating the first drive plate; an electrically driven motor operable to rotate the first drive plate; a mechanically driven motor operable to rotate the first drive plate; a motor selection member configured to switch between the electrically driven motor and the mechanically driven motor.
 13. The air compressor of claim 12, wherein the motor selection member is configured to control a clutch.
 14. The air compressor of claim 12, wherein the plurality of first pistons are positioned on separate ones of the plurality of lobes at different locations relative to top dead center on the plurality of lobes.
 15. The air compressor of claim 12, further comprising: a second drive plate having a plurality of lobes arranged circumferentially; a plurality of second pistons circumferentially spaced apart and in contact with the plurality of lobes of the second drive plate; wherein the second drive plate is driven by one of the electrically driven motor and the mechanically driven motor.
 16. A method of generating compressed air, comprising: providing a housing, at least one drive plate comprising a plurality of lobes arranged circumferentially, a plurality of pistons each contacting one of the plurality of lobes at different locations relative to top dead center, and at least one motor; rotating the at least one drive plate to move the plurality of pistons radially to generate a volume of compressed air in the housing.
 17. The method of claim 16, wherein the at least one motor comprises an electrically driven motor and a mechanically driven motor, the method comprising switching between the electrically driven motor and the mechanically driven motor based on a rotation speed of the mechanically driven motor.
 18. The method of claim 17, further comprising a pulley and drive shaft coupled to the at least one drive plate, wherein the mechanically driven motor is coupled to the pulley with a belt.
 19. The method of claim 17, wherein the electrically driven motor is coupled to the at least one motor with a drive shaft.
 20. The method of claim 17, further comprising a controller and a clutch, the controller operating the clutch to switch between the electrically driven motor and the mechanically driven motor as a power source for rotating the at least one drive plate. 